Production of benzonitrocyclic ketones



I pentanone) A 2,898,376: Patented Aug 5 1 2,898,376- H PRODUCTION OF BENZONITROCYCLIC KETONES No Drawing. Application March 1, 1957 Serial No. 643,238

2 Claims. (Cl. 260--'590) Our invention relates to the production of benzonitrocyclic ketones and more particularly it relates to a process for production of benzonitrocyclic ketones by reaction of a benzocyclic ketone with an alkyl nitrate in the presence of a basic catalyst.

In a paper by Shriner et al., Journal of the American Chemical Society, volume 55, page 4652 (1933), there is described a process for nitration of a-tetralone employing octyl nitrate as the nitration agent and alcoholic potassium ethoxide as the basic catalyst. The process resulted in only very low yields of the potassium salt of B-nitro-a-tetralone.

We have now discovered a process for nitration of benzocyclic ketones wherein a benzene ring is fused to an alicyclic ketone having at least one hydrogen attached to the carbon atom alpha to the ketone substituted carbon atom employing alkyl nitrates as the nitrating agent whereby exceptionally high yields are obtained. Our new United States Patent 0 process thus provides a convenient means for obtaining nitro compounds previously obtained only with difficulty.

Our new process consists essentially of reacting an alkyl nitrate with a benzocyclic ketone in the presence of a potassium alkoxide employing a nonalcoholic solvent at a temperature below about 10 C. The desired benzonitrocyclic ketones are produced in the reaction mixture as the potassium salt which can be decomposed by acidification to obtain the free benzonitrocyclic ketones.

In carrying out our process, we react a benzocyclic ketone such as, for example, a-indanone (benzocyclo- 1,3-indandione (benzocyclopentanedione, m-tetralone (benzocyclohexanone), benzosuberone (benzocycloheptanone), benzocyclooctanone, etc., with an alkyl nitrate such as, for example, ethyl nitrate, propyl nitrate, butyl nitrate, amyl nitrate, etc., in the presence of potassium alkoxide such as, for example, potassium ethoxide, potassium t-butoxide, etc., and a non-alcoholic inert solvent such as, for example, ether, tetrahydrofuran, toluene, hexane, etc. We prefer to react the benzocyclic ketone with amyl nitrate in the presence of potassium t-butoxide using tetrahydrofuran as a solvent.

As indicated above, the presence of alcohol in our reaction mixture is detrimental to the production of the benzonitrocyclic ketones desired. Only a relatively minor amount of alcohol is suflicient to substantially reduce the yield of the desired product to a range of about 2.5 to 5.0%.

As indicated above, we carry out our new process at a temperature below about 10 C. and preferably at a temperature of about -30 C. We also prefer to carry out our reaction by first adding the benzocyclic ketone to the base and then adding the alkyl nitrate to the mixture of ketone and base. Following addition of the ketone to the base at the preferred temperature of about 30 C., the nitrate is then added to the mixture. As soon as the additon of the nitrate is complete, the reaction mixture is allowed to warm to room temfinal product. Theoretically, one mole of alkyl nitrate,

one mole of benzocyclic ketone and one mole of base would be required; however, we prefer to employ an excess of base as indicated above, and we have employed and prefer to employ an excess of base up to about 65% over that amount theoretically required since we have found that such excesss tends to increase the yield of the final product.

As mentioned above, we prefer to bring the reactants together in a particular order since we have found that our preferred order of addition of reactants tends to increase the yield. We prefer to first add the benzocyclic ketone to a solvent solution of the base and then add the alkyl nitrate to the mixture of benzocyclic ketone and base. We believe that in so adding the reactants, we tend to increase the yield by minimizing the tendency of unfavorable equilibrium conditions to form and minimizing possible loss of alkyl nitrate due to decomposition upon prolonged contact of the nitrate with the base.

The following examples are offered to illustrate our invention, however, we do not intend to be limited to the specific procedures, materials, or conditions shown. Rather, we intend to include within the scope of this application, all equivalents obvious to those skilled in the art.

Example I A solution of 18.5 grams of potassium t-butoxide in ml. of tetrahydrofuran was cooled to 30 C. and a solution of 14.6 grams of a-tetralone in 60 ml. of tetrahydrofuran was added dropwise over a period of thirty minutes. Following addition of the a-tetralone, a solution of 14.6 grams of amylnitrate in 35 ml. of tetrahydrofuran was added dropwise over a period of 30 minutes at the temperature of -30 C. The reaction mixture was then allowed to warm to room temperature with stirring and then filtered. The residue was washed successively with 60 ml. of tetrahydrofuran, 50 ml. of methanol and 50 ml. of ether and then dried in vacuo over sulfuric acid to obtain 10.6 grams of potassium 2-nitrotetralone, a yield of 46.2%. The product was crystallized from hot ethanol.

Analysis.Calculated: C=52.4%, H=3.49%, N =6.11%, K=17.03%. Found: C=52.10%, H=3.49%, N=6.07%, K=17.00%.

Example II Potassium Z-nitrotetralone was dissolved in water and 5% hydrochloric acid added dropwise at 0 until a pH of 3 was obtained. A precipitate was formed which was filtered, air dried and recrystallized from 70% methanolwater solution to obtain pale yellow crystals of .Z-nitrotetralone melting at 72-73" C.

Analysis.Calculated: C=62.92%, H=4.74%, N =7.31%. Found: C=63.02%, H=4.94%, N=7.40%.

Example 111 a-Indanone was nitrated according to the procedure set forth in Example I to obtain potassium 2-nitro-1- indanone in the form of hygroscopic purple crystals. The potassium 2-nitro-l-indanone was acidified to obtain 2-nitro-l-indanone.

Now having described our invention, what we claim is:

1. A process for the production of Z-nitro-l-tetralono which comprisesaiiding amyi nitrate to a mixture of 11- tetralone and an excess of potassium t-butoxide in solution in tetrahydrofuran at a temperature of about 30 C. to obtain potassium 2-nitro'1-tetralone, acidifying the potassium salt to obtain 2-nitro-1-tetralone.

f 2. A process for production of Z-nitro-l-indanone which comprises adding amyl nitrate to a mixture of aindanone and an excess of potassium t-butoxide in a solu- References Cited in the file of this patent Horne et al.: J. Am. -Chem. 300., vol. 55, pp. 4652-4 

1. A PROCESS FOR THE PRODUCTION OF 2-NITRO-1-TETRALONE WHICH COMPRISES ADDING AMYL NITRATE TO A MIXTURE OF ATETRALONE AND AN EXCESS OF POTASSIUM T-BUTOXIDE IN SOLUTION IN TETRAHYDROFURAN OF A TEMPERATURE OF ABOUT -30* C. TO OBTAIN POTASSIUM 2-NITRO-1-TETRALONE, ACIDIFYING THE POTASSIUM SALT TO OBTAIN 2-NITRO-1-TETRALONE. 